MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Contacts:
Lynn Chandler, NASA/Goddard Space Flight Center, Greenbelt, Md
(301) 614-5562
Mary Beth Murrill, JPL (818) 354-6478
FOR IMMEDIATE RELEASE
April 5, 2000
NASA-EUROPEAN MEASUREMENTS SEE SIGNIFICANT ARCTIC OZONE LOSS
Ozone losses of more than 60 percent have occurred in the
Arctic stratosphere near 60,000 feet (18 kilometer) in one of the
coldest winters on record. This is one of the worst ozone losses
at this altitude in the Arctic.
Investigations into the Arctic stratosphere have provided
better insights into the processes that control polar ozone.
These insights considerably add to scientists' ability to predict
ozone levels in the future as chlorine levels decline as a result
of the Montreal Protocol, and as greenhouse gases increase.
Climate change in the stratosphere will likely enhance ozone
losses in the Arctic winter in the coming decades, even as the
amount of chlorine introduced into the atmosphere is decreased,
researchers say.
This winter, the NASA sponsored SAGE III Ozone Loss and
Validation Experiment (SOLVE) and European Union sponsored Third
European Stratospheric Experiment on Ozone (THESEO) obtained
measurements of ozone, other atmospheric gases, and particles
using satellites, airplanes, large, small and long duration
balloons, and ground-based instruments.
Scientists from the United States joined with scientists
from Europe, Canada, Russia and Japan in mounting the biggest
field measurement campaign yet to measure ozone amounts and
changes in the Arctic stratosphere. The activities were conducted
from November 1999 through March 2000. The total amount of
information collected by the international campaign this winter
is greater than the information collected in any past polar
measurement campaign. Most of the measurements were made near
Kiruna, Sweden with additional measurements being made from
satellites and a network of stations at mid- and high- northern
latitudes.
During the winter of 1999-2000, large ozone losses were
observed in the Arctic lower stratosphere, measured by a number
of instruments and techniques, including a National Oceanic and
Atmospheric Administration ozone instrument aboard the high
altitude NASA ER-2 aircraft, a civilian variant of the U-2
reconnaissance plane.
"Measurements from the NASA ER-2 show ozone in the Arctic
region decreasing by about 60 percent between January and mid-
March," said ER-2 co-project scientist Dr. Paul A. Newman of
NASA's Goddard Space Flight Center, Greenbelt, Md.
These measurements are comparable to the large chemical
losses at this altitude observed in several winters in the mid-
1990s. The effect on total column ozone was slightly mitigated by
the fact that reductions in ozone were smaller above 20
kilometers (66,000 feet). Spacecraft observations by NASA's Total
Ozone Mapping Spectrometer-Earth Probe showed a clear ozone
minimum over the polar region during February and March. The
average polar column amounts of ozone for the first two weeks of
March were 16 percent lower than observed in the early 1980's.
High altitude clouds (at about 18 kilometers or 60,000 feet)
that exist only at the poles are called "polar stratospheric
clouds" or PSCs. They play a unique role in atmospheric ozone
loss. The visually beautiful, opalescent clouds form only at the
cold temperatures found at the poles. These clouds help trigger
the conversion of chlorine from relatively non-reactive forms to
a form (chlorine monoxide, or ClO) that, in combination with
sunlight, destroys ozone.
PSCs were observed to extend widely over the Arctic region
from early December to early March. "We were somewhat surprised
to see PSCs so early in December," said Dr. Mark Schoeberl, who
was the SOLVE co-project scientist for observations made from
NASA's DC-8 aircraft. "Some of the PSC types and their locations
which we observed in December did not fit within our current
understanding." The last PSCs were observed on March 8 by
instruments aboard the DC-8, and on March 15 by satellite.
The polar stratosphere temperatures were extremely low over
the course of this last winter. PSCs can only form in these low
temperature regions. At 20 kilometers (66,000 feet) on Jan. 28,
the area covered by temperatures low enough to form PSCs was 14.8
million square kilometers (5.7 million square miles), which is
larger than the United States. This is the largest-area coverage
recorded in more than 40 years of Northern Hemisphere
stratospheric analyses.
"The polar stratospheric clouds covered a larger area, and
persisted for a longer period of time, than for any other Arctic
winter during the past 20 years. These conditions heighten our
concern regarding possible couplings between climate change and
stratospheric ozone depletion," said ozone researcher Dr. Ross
Salawitch of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The mixing of polar air into middle latitudes, both during
the winter and as the polar circulation broke down in late March,
influences ozone levels over the populated middle latitudes.
Dilution of ozone-depleted air into latitudes is a major
contributor to the long-term mid-latitude decline. These mixing
processes have been studied during SOLVE/THESEO-2000 and detailed
analysis of these processes continues.
For further information visit the SOLVE web site at
http://cloud1.arc.nasa.gov/solve/ . For supporting images see:
http://www.jpl.nasa.gov/pictures/solve or
http://svs.gsfc.nasa.gov/imagewall/solve.html .
JPL is managed for NASA by the California Institute of
Technology, Pasadena.
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